go.talks/2013/concurrency: decrease length of the daisy-chain

Fixes golang/go#6602

R=golang-dev, minux.ma, r
CC=golang-dev
https://golang.org/cl/14763043
diff --git a/2012/concurrency/support/daisy.go b/2012/concurrency/support/daisy.go
index 9428453..de4889c 100644
--- a/2012/concurrency/support/daisy.go
+++ b/2012/concurrency/support/daisy.go
@@ -9,7 +9,7 @@
 }
 
 func main() {
-	const n = 100000
+	const n = 10000
 	leftmost := make(chan int)
 	right := leftmost
 	left := leftmost